Shadows refer to the darker areas in a photo where less light is reaching the subject. They are created when an object blocks the light source, causing a contrast between the illuminated and non-illuminated parts of the scene. Shadows add depth, dimension, and visual interest to a photograph, enhancing the overall composition. By capturing shadows, photographers can create dramatic and atmospheric effects, emphasizing texture and form. Therefore, the given answer "shadows" correctly identifies the darker areas of a photo.